Control of choke coil with switching-in tap transformer



7 1,623,839 Aprll 5, 1927. A. HUNDT CONTROL OF CHOKE COIL WITH SWITCHING IN TAP TRANSFORMERS Filed Aug. 22, 1925 F igl.

Invenror: Albert Hundh 9 His Arrorneg Patented Apr. 5, 1927.

UNITED ,s A

TES' PATENT OFFICE.

ALBERT norm, OFKAnLsHOns'r, \GERMANY, ASSIGNOR 'ro" GENERAL ELECTRIC COMPANY, A CORPORATION or NEwYOnx;

CONTROL OF CHOKE COIL WITH SWITCHING-IN TAP TRANSFORMER.

Application filed August a, 1925, Serial no.

In order to eilectthe change-over from one switch step to the other in tap transformers for applying a step by step varying voltage to a translating device without interruption of the circuit, use has hereto forebeen made of a choke'coil, the supply line for the translating device bein con nected to the mid-point of the winding of tlrechoke coil, while the two ends of the winding are connected to two neighboring. taps of the transformer. Thus half the load current. flows continuously through the two portions of the winding and the step voltage is --likewise halved. In the change-over from one step to the other one half of the choke. coil is cut out and the entire current flows temporarily through the other half of the winding until the change-over is com pleted. With this switching method "half the load current is interrupted and again out in with considerable spark formation at the switch contacts, and the supply voltage is suddenly altered by the value of the step voltage. This disadvantage is remedied by the invention in that there is provided a relative ,movement between the magnetic material or core and the. halves of the choke coil, as for example, by the provision of means whereby the magnetic material or core is mounted so as to be displaced and is I pushed during theswitching process out of one half of the coil into the other and vice versa.

The result of this isthat the half of the choke coil in which the ironoore is located can receive only a very slight current, while the greater portion of the current is compelled to flow through the other half of the choke coil. The voltage distribution takes place in reverse-'manner. The current is gradually forced by the movement of the iron core'from' the one half of the coil into the other, while the voltage distribution is gradually displaced in the contrary direc- 'tion Thus, in thechange over only ,a very slight. current is interrupted and cut -in again, and moreover the supply voltage is f altered continuously.

Fig.1 is a very simplified diagram of a motor control scheme 1n accordance -Wltl'l 3 the invention, 2 is a diagrammatic representation of the manner in which the 1ro ncore of the choke coil is disposed in ntimate relation with one half and then with the other half of the choke coil, Fig. 3 and 51,886, and in Germany September}, 1924.

Fig. 5 are modifications of the arrangement of Fig. 2, Fig. 4 is a detail showing one method of varyin the reactance of the halves of the cho e coil alternately, and Fig. 6 is another detailjshowing in very simple diagram an arrangement whereby the step by step switching operations and the movements of the iron cores of the choke 'coil halves are synchronized.

Fig. 1 shows diagrammatlcally a step transformer, with the primary winding Z and the secondary winding m, which feeds .a motor 1:. By means of the switches a to g to change over to the second switch step,-

the switch a is opened and the switch a closed." a v Fig. 2 shows the choke coils h and z with the displaceable iron core n. It the core at is located, asshown, in the coil-h, the load current flows through the switch a and the in the coil 11 in a similar manner until the coil z, while there is very little current core'is completely pushed into the coil i, and

practically the entire motor current flows in coil h. Simultaneously the voltage applied to themotor k has gradually increased by the voltage of the step I. v The switch a can now be opened without the formation of sparks at the'contact thereof and the switch 0 can be closed without the formation of sparks. Hereupon the same action with step II can be begun anew.

Ifnow the opening and closing-of the switches and the displacement of the iron core is positively controlled in a suitable manner, aycontinuous regulation of thesupply voltage results almost without any interruption of current.

. Instead of the iron core 11, a hollow disn placeable iron body 0 (Fig. 3)'enclosing the coil 71.. or the coil i can also be employed.

Further, the core n and the iron bodvo can also be emplo ed-s'imultaneously, whereth'ereactance'ls still further diminished. In Fig. 4: is shown the arrangement of two iron cores p and g which for the same purpose are suspended from a balance beam 2' and alternately dip into the coils h and 2', respectively.

Fig. 5 shows a device in which the two coils h and i are enclosed by the two iron yokes t for the purpose of keeping as low as possible the reactance ofthe coil inwhich the core happens to be.

The arrangement described for singlephase current can naturally be suitably employed also for polyphase current.

In Fig. 6 I have shown in very diagrammatic form an arrangement whereby the movement of the cores forthe choke coils is caused to proceed in accordance with the switching operation from one tap voltage to another. The controller 10, having the switch contacts a to g thereon arranged to close successively as the controller is turned,

has mechanically connected thereto a cam 11 and another cam 12 which is driven from the cam 11. These cams have projections thereon which cooperate .withthe projection 18 on the walking beam 7" so as to tilt the walking beam back and forth and thus move the cores p and 9 into and out of their respective choke coils as the-controller is turned. The variation in the choking effect of each choke coil half is thus coordinated properly with the opening and closing of the switches a to g as set forth previously.

WhatI claim as new and desire to secure I by Letters Patent of the'United States, is:

1; A control for a translating device sup- V plied with a'variable voltage through ta 5 of a transformer in which the translating evice is connected to a point between two-sub stantially similar .connected choke coils and the ends of such coils are connected to tap sw tches in such manner that a progressive operation of the switches first places one of the similar connected choke coils in series with the translating device, then the choke coils across taps of thetransformer, then the; other of the choke coils in series with the ftra'nslatlng device, characterized by the provision of means for alternately varying the reactance ot the choke 60118 as the switches are progressively operated for the purpose specified.

2. A control .for a translatingdevice supplied with a variable voltage through taps of a transformer in which the translating deviceis connected to a point between two substantially similar connected choke coils and the ends of such coils are connected to tap switches in such manner that a progressive operation of the switches first places one as the tap switches are progressively opera'ted, for the purpose specified. 3. A control for a translating device supplied with a variable voltage through taps of a transformer in which the translating device is connected to a point between two substantially similar connected choke colls tap switches in such. manner that a pro ressive operation ofthe switches first p aces one of the choke coils in series with the translating device, thenthe'choke coils across taps of the transformer, then the other of the choke coils in series with the translating (leand the ends of such coils are connected to i a vice, characterizedby the provision of a movable magnetic elementfor each of said coils and means for alternately moving said elements lnto and outof intimate relation with their respective ,coils as the tap switches are progressively operated, for'the purpose specified.

In witness whereof, I have hereunto 'set my hand this 6th day of August, 1925.

Y 5 ALBERTHUNDT. 

